Hi,
I have laboured over the functor business and can get transactors to
work. However I need to pass a stream object to a transactor but this
results in all kinds of problems. I have included my program below which
works without the stream. I have tried to incorporate a stream using
your explicit constructor in the tutorial. I don't understand this line
from the section on "How Transactors Work"-
explicit HelloFunctor(ostream &S) : Stream(S) {}
My compiler and I agree that HelloFunctor is not derived from Stream(S).
Can anyone provide more detailed explanation on what this line really does.
Thanks in advance.
Regards,
Rabin
My compiler is gcc 4.1.1 on Fedora 6.
My program:
#include <iostream>
#include <pqxx/pqxx>
#include <pqxx/connection>
#include <pqxx/nontransaction>
#include <pqxx/transactor>
#include <pqxx/result>
using namespace std;
using std::string;
using namespace PGSTD;
using namespace pqxx;
class alphaTransactor:public transactor<transaction<read_committed> >
{
public:
//Copy Constructor?
alphaTransactor() : transactor<transaction<read_committed>
>("genericTransactor")
{}
//Becomes functor
void operator()(transaction<read_committed> &T)
{
qResultSet = T.exec(qString);
}
void on_commit()
{
for (result::size_type indxi=0; indxi != qResultSet.size();
++indxi)
{
for (result::tuple::size_type indxj = 0; indxj !=
qResultSet.columns(); ++indxj)
{
cout << qResultSet[indxi][indxj] << "\t";
}
cout << "\n";
}
}
void setQueryString(string setTo)
{
qString = setTo;
}
private:
result qResultSet;
string qString;
};
int main ()
{
string inputQuery;
cout << "Please input query string: ";
getline(cin, inputQuery);
try
{
connection Conn("dbname=db001 user=rabin03");
cout << "Connected to " << Conn.dbname() << endl;
//Creation of instance of alphaTransactor does not seem
neccessary in the tutorial! - However below -
alphaTransactor * betaTransactor = new alphaTransactor;
betaTransactor->setQueryString(inputQuery);
//Use of 'transactor' instead of 'transaction'
Conn.perform((*betaTransactor));
}
catch (const sql_error &e)
{
cerr << "SQL error: " << e.what() << endl
<<"Query was: " << e.query() << "" << endl;
return 1;
}
catch (const exception &e)
{
cerr << "Exception: " << e.what() << endl;
return 2;
}
catch (...)
{
//All errors not caught above
cerr << "Unhandled exception" << endl;
return 3;
}
return 0;
}
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